Tornado Alley, May Third, Nineteen Ninety-Nine
Near Oklahoma City, Oklahoma
A Doppler on Wheels research radar measured winds in the Moore, Oklahoma, tornado of May third, nineteen ninety-nine at roughly three hundred miles per hour, the highest wind speed ever recorded within a tornado. The instrument that recorded it was a Doppler on Wheels radar unit, positioned close enough to the circulation to obtain a direct reading. The number stood in the scientific literature as a record for years, and it remains the benchmark against which other violent tornadoes are compared.
The tornado touched down near Chickasha in mid-afternoon and carved a path roughly forty miles long through the southwestern suburbs of Oklahoma City, through Moore and Midwest City, before lifting near Midwest Boulevard. The outbreak that day produced more than sixty individual tornadoes across central Oklahoma and south Kansas. The May third tornado alone killed thirty-six people and destroyed or damaged more than eight thousand homes.
Oklahoma sits at the geographic center of what meteorologists call Tornado Alley, the corridor of the Great Plains where warm moist air from the Gulf of Mexico collides with dry air from the Rocky Mountains under the influence of the jet stream. The collisions are most frequent and most violent in spring, when the temperature gradients are steepest. Oklahoma City and its suburbs sit directly in the corridor's heart, and the city has been struck by more significant tornadoes than almost any other metropolitan area in the country.
The response to this geography has not been to leave. Oklahomans build storm shelters, watch the sky in spring with the specific attentiveness of people who have learned when to stop what they are doing, and develop an almost anthropological relationship with the weather. The tornado warning siren is as characteristic a sound of Oklahoma spring as mockingbirds or thunder.
What has changed is the accuracy of the forecasts. The Warning Coordination Meteorologist program at the Norman, Oklahoma, National Weather Service office, the same office that covers the Oklahoma City metro, pioneered many of the advances in tornado warning lead time. The average lead time for a tornado warning in the nineteen seventies was two minutes.
By the nineteen nineties it had reached ten minutes. It continues to improve. The storms have not gotten smaller.
The warnings have gotten better.
